Avian reticuloendotheliosis virus (REV-T) is a replication-defective retrovirus that transforms very immature lymphoid cells and induces a fatal lymphomatosis within 7-10 days. REV-T is the only retrovirus which immortalizes cells and converts them to a tumorigenic state in a helper virus independent fashion. REV-T contains a single oncogene, v-rel, which is distinct from all other known oncogenes and is responsible for transformation. Uninfected vertebrate cells and Drosophila contain a sequence related to the v-rel oncogene. Polyclonal antisera to the v-rel protein synthesized in E. coli immunoprecipitates a phosphoprotein with a molecular weight of 57 kDa which is located in the cytosol of transformed cells. Preliminary studies indicate that the v-rel protein may possess Mn+ dependent protein kinase activity capable of autophosphorylation. One of our specific aims will be to characterize the enzymes activity associated with the v-rel protein. To demonstrate whether the kinase activity is intrinsic to v-rel protein the entire v-rel gene and deletion mutants will be expressed in E. coli and the products assaysed for kinase activity. Deletion mutants which lack kinase activity will also be tested for their ability to transform lymphoid cells in vitro. We will determine whether the transforming protein is a serine/threonine or tyrosine protein kinase. We propose to identify potential cellular substrates of the v-rel kinase. Monoclonal antibodies will be developed to characterize functional domains and identify potential cellular substrates. A correlation has been observed between REV-T provirus copy number, level of v-rel transcription, and extent of immunoglobulin gene rearrangements in REV-T transformed lymphoid cells. We propose to define whether the level of v-rel expression indirectly influences the phenotype of the REV-T transformed lymphoid cells. We propose to identify the produce of the c-rel proto-oncogene and compare its enzyme activity and substrate specificity to the viral transforming protein. The expression of c-rel will also be studied during early avian embryogenesis to define its role in the control of cell proliferation and differentiation.